Inverted pyramidal neurons in chimpanzee sensorimotor cortex are revealed by immunostaining with monoclonal antibody SMI-32.

We used the monoclonal antibody SMI-32 to label pyramidal cells of sensorimotor cortex in two chimpanzees. The majority of the pyramidal cells had typical vertically oriented apical dendrites that extended towards the pial surface. A small population of pyramidal cells varied from this orientation, so that the apical dendrites were 20 degrees or more from radial, and were often inverted, extending away from the pial surface. When numbers of non-inverted and inverted pyramidal cells were compared, less than 1% were found to be inverted.